1. Field of the Invention
The present invention relates to the field of power supplies and, more particularly, to programmable power supplies.
2. Background Information
Voltage regulators are used to provide a controlled, stable output voltage to a load. A voltage regulator receives power from an unregulated power source and provides power to a load at a predetermined output voltage. A typical regulator includes a control circuit that compares a reference voltage with a feedback voltage proportional to the output voltage from the regulator to develop an error signal, with the control circuit controlling the regulator to provide more or less current to the load to reduce the error signal, thereby forming a closed loop system. Such regulators may be of any of various types, such as linear regulators and switching regulators, including step-up and step-down switching regulators.
Programmable voltage regulators are used to provide output voltages that can be set to provide the output voltage required. Digitally programmable voltage regulators are set by digital signal values that represent the desired output voltages. The MAX1638 high-speed step-down controller with synchronous rectification for CPU power, manufactured by Maxim Integrated Products, is an example of a digitally programmable voltage regulator that provides output voltage levels set by received digital values.
In a typical application, a programmed increase in the output voltage of the programmable regulator results in a momentarily high current drain from the power source supplying power to the digitally programmable voltage regulator. Some power sources, such as batteries, have relatively high internal impedance and thus are not able to supply a load current substantially higher than the normal range of load currents, even for a brief period. The voltage of such a power source can drop momentarily to a low level when the power source is subjected to the high current drain from supplying power to the digitally programmable voltage regulator whenever the set-point voltage is increased.